Electrohydraulic metal forming system and method



ELECTROHYDRAULIC METAL FORMING SYSTEM AND METHOD Filed May 24, 1963 LAM I 1 I l |4 \T LO.

1 I 6 3,8 1,8 3 2 j zo 9 1 l I I 1 3O 26 28 WITNESSES INVENTORS 32am Louis C Grove,Jr.

and Robert T. Inn {WM BY :7

ATTOR EY United States Patent ice 3,253,442 ELECTROHYDRAULIC METAL FORMING SYSTEM AND METHOD Louis C. Grove, Jr., Bloomington, and Robert T. Innis,

Ellettsville, Ind, assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., -a corporation of Pennsylvania Filed May, 24, 1963, Ser. No. 283,033 Claims. (Cl. 72-56) The present invention relates to electrohydraulic metal forming systems and methods, and more particularly to such systems and methods in which an arc discharge induces a hydraulic pressure front for metal forming action.

In electrohydraulic metal forming, the metal piece to be formed is fixed 011 a die or similar object and this combination is then disposed in a liquid filled container.

Energy storage means such as a capacitor bank are then operated to produce an arc discharge between a pair of electrodes which are also submerged in the liquid in a suitable location. Hydraulic pressure generated by the arc discharge impinges on the metal piece and produces the desired metal forming action.

One of the problems encountered in electrohydraulic metal forming systems is that ordinarily the liquid in which the system are electrodes are disposed has relatively high dielectric strength and thus prevents or substantially impedes the striking of an arc. One manner in which this problem can be countered is through the introduction of a fuse member between the submerged arc electrodes so that interelectrode current can be readily initiated through the fuse member and further so that an arc discharge continues the interelectrode current flow instantaneously after fuse blowing from overheating. The fuse thus initially provides a highly conductive path be tween the electrodes so that excessive voltage is not rea quired to establish an arc in the normally high dielectric medium or liquid.

It is important, however, that an electrohydraulic metal forming system not only be able to produce a hydraulic metal forming arc, but that it be able to do so efliciently in terms of operating advantages. Hence, in most-cases metal forming apparatus has good utility only if it is effiei ently susceptible to repetitive operations and, if a hydraulic metal forming system such as the described system requires cumbersome or time consuming action such as replacing a fuse in order to prepare the system for a new or repeat arc strike, it is not as efiicient as it desirably should be.

Thus, in accordance with the broad principles of the present invention, there is provided an electrohydraulic metal forming system which efficiently provides for repetitive metal forming operations and which comprises for this :purpose energy storage means, or a bank of capacitors, connected by switching means to a pair of arc electrodes submerged in a relatively high dielectric liquid. Arc striking is enabled through controlled disposition of a pressure released relatively low dielectric medium between the submerged electrodes. The invention also encompasses method steps directed to efficient electrohydraulic metal forming. Such steps include applying an electric potential across arc electrodes submerged in a relatively high dielectric liquid and disposing in the space between the arc electrodes a relatively low dielectric medium so as to enable an arc to be struck.

it is, therefore, an object of the invention to provide a novel electrohydraulic metal forming system which efliciently provides for repetitive metal forming operations.

It is another object of the invention to provide a novel electrohydraulic metal forming system which efliciently provides for the disposition of a relatively low dielectric medium between arc electrodes submerged in a relatively 3,253,442 Patented May 31, 1966 high dielectric liquid so as to. enable an arc to be struck between the electrodes. 4

A further object of the invention is to provide a novel electrohydraulic metal forming method which efliciently provides for repetitive metal forming operations.

These and other objects of the invention will become more apparent upon consideration of the following detailed description along with the attached drawing, in which:

The single figure shows a schematic view of an electrohydraulic metal forming system constructed and operable in accordance with the principles of the invention.

More specifically, there is shown in the drawing an electrohydraulic metal forming system 10 comprising an energy storage source 12 connected by switching means 14 to spaced electrodes 16 and 18 which in turn are suitably .disposed and supported in a container 20. In this example, horizontal beams 22 and 24 attached to the two side walls of the container 20' are employed to support'the electrodes 16 and 18 with the desired spacing therebetween.

Disposed on bottom wall 26 of the container 26 is a die 28 or the like. A sheet 30 of metal having suitable thickness and contour is in turn disposed and preferably suitably fixed on the die 28 so as to be formable against the die 28 upon the imposition of a hydraulic pressure front thereagainst. Thus, the container 20 holds a given volume of liquid 32 (such as water) which is the medium through which the pressure front can be advanced. Such hydraulic pressure is caused by an arc discharge between the electrodes 16 and 18 and can carry enough energy to produce the desired metal forming'action against the die 28.

In order to provide the energy necessary to initiate and sustain an arc discharge capable of producing the peak hydraulic pressure front required for metal forming, the energy storage source 12 includes one or more capacitors 34 but preferably a bank of capacitors 34 which are energized from a suitable power source (not shown). While the capacitors 34 are being charged to the desired energy level, the switching means 14 are disposed in an open position. Upon completion of the capacitor charging operation, the switching means 14 can be closed so as to apply the developed capacitor potential across the electrodes 16 and 1S.

On the other hand, in some applications, the switching means 14 can be closed while the capacitors 34 are being charged so that the potential across the electrodes 16 and 18 rises generally in conformity with the development of potential across the capacitors 34. In any event, once peak voltage or potential is applied across electrodes 16 and 18, the relatively high dielectric strength of the liquid 32 normally prevents or substantially impedes the striking of an are between the electrodes 16 and 18.

When it is desired to strike an arc, the liquid in the space between the electrodes 16 and 18 is substantially displaced by a relatively low dielectric strength medium or gas (such as air) which is transported through suitable means such as a conduit 36 from a pressurized source (not shown). The conduit 36 can extend through the container 20 and supporting beam 22 with an exit end portion 38 thereof extending through the electrode 18. However, the conduit 36 or similar transport channel can be disposed structurally in any suitable manner so long as the exit end portion thereof is effective in disposing the low dielectric medium in the space between the electrodes 16 and 18.

In order to control the flow of pressurized air or other medium to the space between the electrodes 16 and 18, suitable valve means such as an ordinary electromagnetically operated valve 40 can be connected to the conduit 36 for controlling the flow through the latter member.

Thus, once the necessary peak potential is applied across the electrodes 16 and 18, the valve 40 can be actuated to release under suitable pressure or to introduce the air or other low dielectric medium into the space between the electrodes 16 and 18. With rapid ionization of the low dielectric strength medium between the electrodes 16 and 18 under the influence of the potential thereacross, an arc is struck between the electrodes 16 and 18 and the ensuing hydraulic pressure front which advances to the metal sheet 30 is effective in producing the desired metal forming action.

The switching means 14 can then be reopened, the valve means 40 can be closed to terminate the flow through the conduit 36 and switching means 42 can be closed to discharge the remaining charge on the capacitors 34through discharge resistor 44 if it is desired to terminate the operation of the equipment. On the other hand, the capacitors 34 can be recharged and a new metal forming operation on a new metal sheet can be readily performed again in the manner previously described. Metal forming operations can thus be efficiently and readily repeated on a continuing basis.

The foregoing description has been set forth only to point out the principles of the invention. Accordingly, it is desired that the invention be not limited by the embodiment described, but, rather, that it be accorded an interpretation consistent with the scope and spirit of its broad principles.

What is claimed is:

1. An electrohydraulic metal forming system comprising energy storage means, means for connecting said energy storage means to a pair of spaced electrodes disposed in a container, said electrodes being submerged in a liquid of relatively high dielectric strength in the container, and means for introducing a gas of relatively low dielectric strength between said electrodes to initiate a discharge therebetween.

2. An electrohydraulic metal forming system comprising energy storage means, means for connecting said energy storage means to a pair of spaced electrodes disposed in a container, said electrodes being submerged in a liquid of relatively high dielectric strength in the container, a suitably supported conduit having its outlet end disposed for introducing in the space between said electrodes a medium having a lower dielectric strength than said liquid, said lower dielectric strength medium being transportable under pressure through said conduit, and means for controlling the flow of said low dielectric medium through said conduit.

of electrodes through switching means, means for sup-- porting said electrodes in suitably spaced relation in a container, said container holding a relatively high dielectric liquid in which said electrodes are submerged, a suitably supported conduit having its outlet end disposed for introducing in the space between said electrodes a relatively lower dielectric medium than said liquid transportable under pressure through said conduit, and means for controlling the flow of said low dielectric medium through said conduit.

4. An electrohydraulic metal forming system comprising a bank of capacitors energizable from a suitable source of power, said capacitor bank connected to a pair of electrodes through switching means, means for supporting said electrodes in suitably spaced relation in a container, said container holding a relatively high dielectric liquid in which said electrodes are submerged, a suitably supported conduit having its outlet end extending through one of said electrodes so as to be disposed for introducing in the space between said electrodes a relatively low dielectric gas transportable under pressure through said conduit, and valve means for controlling the flow of said low dielectric gas through said conduit.

5. An electrohydraulic metal forming system comprising an energy storage source energizable from a suitable source of power, said energy storage source connected through switching means to a pair of electrodes, means for supporting said electrodes in suitably spaced relation in a container, said container holding a relatively 'high dielectric liquid in which said electrodes are submerged, a suitably supported conduit having its outlet end extending through one of said electrodes so as to be disposed for introducing in the space between said electrodes a relatively low dielectric medium transportable under pressure through said conduit, and means for controlling the flow of said low dielectric medium through said conduit.

References Cited by the Examiner UNITED STATES PATENTS 2,559,227 7/1951 Rieber 1l344 3,129,403 4/1964 Harter 113-44 3,163,141 12/1964 Wesley et a1. 113--44 CHARLES W. LANHAM, Primary Examiner.

R. J. HERBST, Assistant Examiner. 

1. AN ELECTROHYDRAULIC METAL FORMING SYSTEM COMPRISING ENERGY STORAGE MEANS, MEANS FOR CONNECTING SAID ENERGY STORAGE MEANS TO A PAIR OF SPACED ELECTRODES DISPOSED IN A CONTAINER, SAID ELECTRODE BEING SUBMERGED IN A LIQUID OF RELATIVELY HIGH DIELECTRIC STRENGTH IN THE CONTAINER, AND MEANS FOR INTRODUCING A GAS OF RELATIVELY LOW DIELECTRIC STRENGTH BETWEEN SAID ELECTRODES TO INITIATE A DISCHARGE THEREBETWEEN. 